Suspension polymerization process and novel compounds for use in said process



Unite States. Patent 2,996,490 SUSPENSION POLYMERIZATION PROCESS ANDNOVEL COMPOUNDS FOR USE IN SAID PROCESS George P. Rowland, Pottstown,and John J. Wolski, Springfield, Pa., assignors to The Firestone Tire &Rubber Company, Akron, Ohio, a corporation of Ohio N Drawing. Filed May12, 1959, Ser. No. 812,575 SCIaims. (Cl. 260-92.8)

This invention relates to the suspension polymerization of vinylchloride to yield resins having good dry plasticizer blending propertiesand good electrical properties, and also to certain novel metallic saltsof alkyl beta-imino dipropionic acid for use in said process.

Vinyl chloride resin compositions are generally made up by initiallymixing the granular resin, liquid plasticizers, stabilizer, pigments,etc. in a ribbon or blade-type mixer until a uniform, granular,free-flowing blend results. The blend is then transferred to fusing andhotworking machinery such as roll mills, Banbury mills, extruders,calenders and the like for working up into the final desired resinproducts. It is highly desirable that a resin so processed shall havethe property, during the initial mixing stage, of rapidly taking up theliquid plasticizer so that the resin appears macroscopically dry, theliquid plasticizer being completely absorbed into the pores of the resingranules. If this state is not achieved during the preliminary mixing,considerable difficulties will be encountered in subsequent processing.Any plasticizer not absorbed into the resin lubricates the granules sothat they are not efliciently homogenized in the hotworking machinery,which results in excessive power consumption and in fish-eyes and otherdiscontinuities in the finished products. Very few resins on the marketat present have good plasticizer absorption performance as aboveoutlined.

Accordingly, it is an object of this invention to provide a novelprocess for the production of vinyl chloride resins having excellentplasticizer absorption characteristics.

Another object is to provide such a process in which use is made of theavailable suspension polymerization apparatus and techniques.

A further object is to provide new chemical compounds for use in theprocess above outlined.

SYNOPSIS OF THE INVENTION The above and other objects are secured, inaccordance with this invention in a process in which vinyl chloride, ora mixture thereof with other unsaturated compounds copolymerizabletherewith, is polymerized in aqueous suspension in the presence ofcertain bivalent metal salts of alkyl beta-imino dipropionic acidshaving the formula 1 alkyl-N wherein: alkyl represents an alkyl group offrom 8 to 16 carbon atoms, and Me represents a metal atom which may bebarium, strontium, calcium, zinc or tin.

The resins so produced have excellent plasticizer-absorption properties.

THE ALKYL BETA-IMINO DIPROPIONIC ACID SALTS Referring to Formula 1above, by far the preferred metallic component Me for these compounds isbar- Patented Aug. 15, 1961 ium, followed by strontium, calcium, zincand tin in decreasing order of preference. With respect to the radicalalkyl, the preferred and most convenient radical is the n-dodecylradical, the alkyl beta-imino dipropionic acid corresponding to thisvalue being conveniently available as lauryl beta-imino dipropionicacid, in which the lauryl groups are the mixed radicals containingprincipally dodecyl radicals but also some higher (e.g. tetradecyl) andlower (e.g. octyl and decyl) radicals, derived by the reduction ofcoconut oil fatty acids. The compounds are readily prepared by reacting,in aqueous solution, the sodium, ammonium, or other Water-soluble salt(2) of an alkyl beta-imino dipropionic acid with a chloride or otherwater-soluble salt of barium, strontium, calcium, zinc or tin, thefollowing reaction taking place:

+MeC12- CH2 CH2" 0 0 0 N9.

The desired insoluble salt is recovered by filtration, centrifugationand the like. Specific exemplary compounds under Formula 1 above arebarium dodecyl beta-imino dipropionate, strontium dodecyl beta-iminodipropionate, calcium dodecyl beta-imino dipropionate, zinc dodecylbeta-imino dipropionate, stannous dodecyl beta-imino dipropionate,barium tetradecyl beta-imino dipropionate, barium decyl beta-iminodipropionate, barium 2-ethyl hexyl beta-imino dipropionate, strontiumdecyl betaimino dipropionate, stannous tetradecyl beta-iminodipropionate, and the like. It will be understood that mixtures of twoor more compounds individually coming under Formula 1 are alsocontemplated, for instnace, mixtures of compounds under the Formula 1above in which the alkyl groups are derived from commercial mixtures ofalkylating constituents, for instance the mixed alkyl radicals containedin the alcohols derived by the reduction of the mixtures of fatty acidsoccurring in natural glycerides such as coconut oil, the mixed radicalsderived by dimerization and trimerization of propylene and butylene, oxoprocess alcohols and so on. Like wise mixtures of salts of differentmetals, for instance, mixtures of barium and strontium salts, may beused.

THE POLYMERIZATION In general, the process of this invention follows theordinary suspension polymerization procedure, with the exception thatthe compound of Formula 1 is present. The suspension polymerizationprocess consists in' agitating the vinyl chloride monomer in an aqueousmedium containing a non-micelle-forming protective colloid sespend ingagent. suspending agents suitable for this purpose are hydrophilic highpolymeric materials such as gelatin, starch, carragheen, albumen,agar-agar, gum tragacanth, polyvinyl alcohol, poly acrylic acid,polymaleic acid, methyl cellulose, and the like. The aqueous mediumconstitutes about at least half the entire polymerization mass. Thereaction is promoted by the presence of free-radicalgenerating agentssoluble in the monomer phase of the suspension, such as benzoylperoxide, perben-zoic acid, lauroyl peroxide, p-chlorobenzoyl peroxide,t-butyl hydroperoxide, and the like. In the practice of the presentinvention, there will further be present a salt in accordance withFormula 1 above. The aqueous phase and the monomer phase are agitatedtogether so as to suspend the Me+2NaCl to values such as to initiate thepolymerization reaction, usually on the order of 30'100 C. The monomersin the suspended droplets become polymerized, yielding a suspension ofgranular resin in the aqueous medium. From this aqueoussuspension theresin is isolated by filnation. The amount of the compound (1) used inthe polymerization mass will'generally be upwards of 05%, and preferablyupwards of 1.0%, based on the weight of the monomers in the system. Theupper limit for this concentration is not critical; as as could be addedwithout adverse effect, so far as the operativeness of the process isconcerned However, amounts in excess of 3% will usually be unnecessaryand wasteful from an economic point of view.

It will be understood that the monomeric compositions polymerizedaccording to' this invention may be either unmixed vinyl chloride ormixtures thereof with minor proportions, say not over based on theweight of said mixtures, of one or more other ethylenically unsaturatedcompounds copolymerizable with vinyl chloride. Conversely stated, themixtures should contain at least 80% vinyl chloride by weight.Ethylenically unsaturated compounds copolymerizable with vinyl chlorideare exemplified in vinyl esters on the order of vinyl bromide, vinylfluoride,viny1 acetate, vinyl chloroacetate, vinyl butyrate, other fattyacid vinyl esters, vinyl alkyl sulfonates and the like; vinyl etherssuch as vinyl ethyl ether, vinyl isopropyl ether, vinyl chloroethylether and the like; cyclic unsaturated compounds such as styrene, themonoand polychlorostyrenes, coumarone, indene, vinyl naphthalenes, vinylpyridines, vinyl pyrrole and the like; acrylic acid and its derivativessuch as ethyl acrylate, methyl methacrylate, ethyl methacrylate, etlh-ylchloroacrylate, acrylonitrile, methacrylonitrile, diethyl maleate,diethyl fumarate, and the like; vinylidene compounds on the order or":vinylidene chloride, vinylidene bromide, vinylidene fluorochloride, andthe like; allyl compounds such as allyl acetate, allyl chloride, allylethyl ether and the like; and conjugated and cross-conjugatedethylenically unsaturated compounds such as divinyl ketone and the like.For a fairly complete list of materials known to: polymerize with vinylchloride, reference may be had to Krczil, Kurzes Handbuch derPolymenisations-Technik-II Mehrstoif Polymerization, Edwards Bros. Inc.,1945, pp. 735747, the items under Vinyl chlorid.

THE RESINS PRODUCED IN ACCORDANCE WITH THIS INVENTION Example I v GramsVinyl chlor 60 Water 120 Lauroyl peroxide s 0.2 Gelatin (100 Bloom) 0.4,0.5, 0.6 or 0.8 Barium lauryl beta-imino V dipropionate 0.11, 0.13, 0.15or 0.17

The lauryl substituent isa mixture of alkyl radicals derived from thealcohols produced by the reduction of the mixed fatty acids of coconutoil; predominantly dodecyl groups and tetradecyl groups.

A series of runs was made in accordance with the foregoing recipe, usingeach possible combination oif amounts of gelatin andof barium laurylbeta-imino dipropionate in the several runs. In each run, theingredients, other than vinyl chloride, were charged into a 12-ouncebev- --2,99e,49o I 5 4 v erage bottle and mixed. The vinyl chloride,slightly in excess of the recipe amount, was next charged and allowed tovaporize to purge the free space in the bottle and to reduce the Weightof vinyl chloride to the amount in the recipe. The bottle was thencapped and tumbled in a water bath at 25 C. for one hour, after which itwas tumbled in a water bath at 50 C. for 18 hours. At the end of thisperiod, the bottle was vented and opened, and the polymer was separatedfrom the suspension medium by filtration, washed on the filter withdistilled Water, and dried. The resultant polymer in every case hadexcellent plasticizer-absorbing properties, as observed on a microscopeslide. This observation was made by placing a small quantity of theresin in a thin layer on a microscope slide, adding a drop of dioctylphthal-ate, and placing the slide on the microscope stage. The resin particles could be seen in the microscope to rapidly imbibe the dioctylphthalate. The particle size and shape were very uniform, "the particlesbeing predominantly 280 miorons in diameter and spherical, and the resinwas free from fine and from coarse grains.

Example Il.Vari0us metal salts 'Ihe lauryl substituent' is a mixture ofalkyl radicals derived from the alcohols produced by the reduction ofmixed fatty acids of coconut oil; predominanly dodecyl groups andtetradecyl groups.

A series of runs was made in accordance with the foregoing recipe, usingthe various salts of the imino acid in amounts over the range Indicated.Each run was conducted in accordance with the procedure of Example 1.Good resins from the standpoint of plasticizer-absorption were obtainedin all cases. The optimum ranges for the amount of the salts used,together with the characteristics of the products, are tabulatedherewith.

TABLE I Optimum St Sil i V Amen Range in Description of Product (minutRecipe determined) (grams) as in Example III Calcium 0. 1341.17 Shaggyspheres 175 in diam- 75 e er. Strontiun1 0.13-0.17 Irregular spheres310p. in 65 4 diameter. T111 0.13-0.17 Irregular spheres 140g in 45diameter. Zmc 0.11-0. 17 Irregular spheres 140;]. in 60 diameter.

Example [IL-Large scale run Pounds Vinyl chlorid Water 200 Lauroyl peroV 0.28 Gelatin (type B-100 Bloom) 0.50 Banum lauryl beta-iminodipropionate 1 0.20

The lauryl substituent is a mixture of alkyl radicals derived from thealcohols produced by the reduction of the mixed fatty acids of coconutoil; predominantly dodecyl groups and tetradecyl groups.

A glass-lined steel autoclave provided with an anchor agitator and witha heating and cooling jacket was pro vided for the run. All ingredientsexcept the monomer were charged first. The reactor was then closed, andthe free space therein purged twice with vinyl chloride vapor followedby evacuation. The recipe amount of'vinyl chloride was then charged,agitation commenced, and the temperature raised to F., these conditionsbeing maintained for 19 hours. At the end of this time the unreactedvinyl chloride was vented, and the reaction mass cooled to 25 C. anddischarged. The polymerized vinyl chloride was recovered by filtration,washed on the filter with water, and dried. Following are the propertiesof the product.

TABLE II Relative viscosity (1% solution in cyclohexanone at 25 C.)2.52. Fisheye rating 2 at 3 min. Heat stability (peanut oil180 C.)Failure in 75 min.

Bulking density (gms./cc.) 0.44.

Dry time 8 min.

Hot flow 3 min.

Screen analysis (percent retained):

20 mesh 0%. 40 mesh 0%. 60 mesh 0.4%. 80 mesh 1.0%. '100 mesh 92.0%. 140mesh 3.6%. 200 mesh 1.8%. 325 mesh 0.2%. Percent thru 325 mesh 1.0%.

The properties, other than conventional ones, tabulated above weredetermined as follows:

Heat stability: Grams Resin 100 Dioctyl phthalate 45 Co-precipitatedbarium-cadmium laurate 1 Dibutyltin dilauryl mercaptide 0.5

Fisheye rating:

Resin 100 Dioctyl phthalate 60 Dibutyltin dilauryl mercaptide 3 Theabove ingredients are milled together at 310 F. for 3 minutes, and thensheeted out as a film 13-17 mils in thickness. An S-square inch specimenof the film: is cut out, and the number of fisheyes counted and taken asan inverse measure of the rapidity with which the resin takes up thedioctyl phthalate plasticizer.

Day drier hot flow and dry time: Grams Resin 400 Dioctyl phthalate 200Dibutyltin dilauryl mercaptide 12 -A Day Mixer, which is a steamjacketed double-arm mixer with a capacity of 0.13 cubic feet with twotangential arms rotating at 36 and at 36 and 74 r.p.m. respectively, wasemployed in the test. Jacket temperature was adjusted to 330 F., but thetemperature drifted downwardly during the test, so that the averagetemperature was about 210 F. The ingredients of the recipe were addedcold to the hot mixer over a period of two minutes. Thereafter theprogress of the mixing was watched, and the time at which the mixturefell free from the blades taken as the Hot Flow time. Likewise, smallsamples were removed at one-minute intervals and spread and pressedbetween sheets of paper in an unheated laboratory press under a pressureof 138 psi The length of time in the mixer required before a sample ofthe resin produced no stain on the paper was taken as the Dry Time, andis considered to be an inverse measure of desirable absorption behavior.

The salts of the lauryl beta-imino dipropionic acids 6 ilised in theforegoing experiments were prepared as folows.

A Sodium-lauryl beta-imino dipropionate Deriphat a product of Gen- Aseries of preparations was made in accordance with the above recipe,using the calcium, strontium, barium, stannous and zinc chloridesindividually in the several runs. In each run, the ingredients at A wereplaced in a three-gallon crock provided with a propeller-type agitator,and agitated together until complete solution was achieved. The selectedsalt and Water listed at B were made up into a solution, and slowlyadded to the solution of the ingredients A" with continued stirring. Aprecipitate quickly formed, and the resultant slurry stirred for anadditional five minutes after the last of the ingredients A had beenadded. The slurry was then filtered, and the precipitate thoroughlywashed on the filter with water. The precipitate was then sucked as dryas possible on the filter. The precipitate was then dried in acirculating hot-air oven at 200 F. for 24 hours. Substantiallyquantitative yields Were obtained in every case.

The novel salts of the alkyl beta-imino dipropionic acids employed inthe process of this invention are being separately claimed in adivisional application Serial No. 88,280, filed February 10, 1961.

What is claimed is:

1. Process for polymerizing a monomeric substance selected from thegroup consisting of vinyl chloride and mixtures thereof. with up to 20%,based on the weight of the mixtures, of other ethylenically unsaturatedcompounds copolymerizable therewith which comprises suspending,agitating and polymerizing said monomeric substance in a reaction masscomprising an aqueous solution of a protective colloid, a peroxidecatalyst soluble in said monomeric substance and at least 0.05%, basedon the weight of said monomeric substance, or a salt selected from theclass consisting of the barium, strontium, calcium, tin and zinc neutralsalts of alkyl betaimino dipropionic acids in which the alkyl groupscontain from 8 to 16 carbon atoms.

2. Process for polymerizing a monomeric substance selected from thegroup consisting of vinyl chloride and mixtures thereof with up to 20%,based on the weight of the mixtures, of other ethylenically unsaturatedcom.- pounds copolymerizable therewith which comprises suspending,agitating and polymerizing said monomeric substance in a reaction masscomprising an aqueous solution of a protective colloid, a peroxidecatalyst soluble in said monomeric substance and from 1.0% to 3.0%,based on the weight of said monomeric substance, of baruim laurylbeta-imino dipropionate.

3. Process for polymerizing a monomeric substance selected from thegroup consisting of vinyl chloride and mixtures thereof with up to 20%,based on the Weight of the mixtures, of other ethylenically unsaturatedcompounds copolymerizable therewith which comprises suspending agitatingand polymerizing said monomeric substance in a reaction mass comprisingan aqueous solution of a protective colloid, a peroxide catalyst solublein said monomeric substance and from 1.0% to 3.0%, based onthe Weight ofsaid monomeric substance, of strontium lauryl beta-irnino dipropionate.

4. Process for polymerizing a monomeric substance selected from thegroup consisting of vinyl chloride and mixtures thereof with up to 20%,based on the Weight of the mixturespof other ethylenically unsaturatedcompounds copolymerizable therewith which comprises suspending,agitating and polymerizing said monomeric substance in a reaction masscomprising an aqueous solution of a protective colloid, a peroxidecatalyst soluble in said monomeric substance and from 1.0% to 3. 0%,based on the Weightof said monomeric substance, of calcium laurylbeta-imino dipropionate.

5. Process for polymerizing a monomeric substance selected from thegroup consisting of vinyl chloride and mixtures thereof with up to 20%,based on the Weight of the mixtures, of otherethylenically unsaturatedcompounds co-polymerizable therewith. which comprises suspending,agitating and polymerizing said monomeric substance in a reaction masscomprising an aqueous solution of a protective colloid, a peroxidecatalyst soluble in said monomeric substance and from 1.0% to 3.0%,based on the weight of said monomeric substance, of zinc laurylbeta-imino diproprionate.

6. Process for polymerizing a monomeric substance selected from thegroup consisting of vinyl chloride and mixtures thereof with up to 20%,based on the Weight of the mixtures, of other ethylenically unsaturatedcom-- pounds copolymeriazable therewith which comprises suspending,agitating and polymerizing said monomeric substance in a-reactionmasscomprising an aqueous solutionof a protective colloid, a peroxidecatalyst soluble in said monomeric substance and from 1;0% to 3.0%,based on the Weight of said monomeric substance, of tin lauryl.

beta-imino diproprionate.

7. Process of polymerizing vinyl chloride which com-.

prises suspending, agitating and polymerizing vinyl chloride in areaction mass comprising an aqueous solution References Cited in thefile of this patent UNITED STATES PATENTS 2,528,469 Condo et a1 Oct. 31,1950 2,686,798 Gmitter Aug. 17, 1954 2,833,754 Richards et'al. May 6,1958 2,872,468

Leistner et al. Feb. 3, 1959

1. PROCESS FOR POLYMERIZING A MONOMERIC SUBSTANCE SELECTED FROM THEGROUP CONSISTING OF VINYL CHLORIDE AND MIXTURES THEREOF WITH UP TO 20%,BASED ON THE WEIGHT OF THE MIXTURES, OF OTHER ETHYLENICALLY UNSATURATEDCOMPOUNDS COPOLYMERIZABLE THEREWITH WHICH COMPRISES SUSPENDING,AGITATING AND POLYMERIZING SAID MONOMERIC SUBSTANCE IN A REACTION MASSCOMPRISING AN AQUEOUS SOLUTION OF A PROTECTIVE COLLOID, A PEROXIDECATALYST SOLUBLE IN SAID MONOMERIC SUBSTANCE AND AT LEAST 0.05%, BASEDON THE WEIGHT OF SAID MONOMERIC SUBSTANCE, OF A SALT SELECTED FROM THECLASS CONSISTING OF THE BARIUM, STRONTIUM, CALCIUM, TIN AND ZINC NEUTRALSALTS OF ALKYL BETAIMINO DIPROPIONIC ACIDS IN WHICH THE ALKYL GROUPSCONTAIN FROM 8 TO 16 CARBON ATOMS.